Japanese Patent Publication No. 04-316724 of Nov. 9, 1992 to Nakagaki Seiji et al. (“Seiji Publication”) discloses a centrifugal clutch provided with a clutch release mechanism. FIG. 19 is a cross-sectional view of a centrifugal clutch 200 disclosed in Japanese Patent Publication No. 04-316724. As shown in FIG. 19, the centrifugal clutch 200 is provided with a clutch drum 201, a clutch hub 202 and a plate group 205. The plate group 205 is constituted by a drive plate 204 rotated with the clutch drum 201 and a driven plate 203 rotated with the clutch hub 202. In the centrifugal clutch 200, the distance between a pressurizing plate 210 and a traveling plate 207 is extended by a centrifugal force which acts on a centrifugal ball 208 and a biasing force of clutch spring 206. On the other hand, the distance between the pressurizing plate 210 and the bottom portion of the clutch drum 201 is narrowed. Consequently, the plate group 205 transitions into a pressed contact state.
Clutch spring 206 comprises a compression coil spring in the Seiji Publication. Therefore, it is necessary to separately arrange an end plate 209 receiving the biasing force of the clutch spring 206 so as to face the traveling plate 207. The end plate 209 and the traveling plate 207 must have relatively high rigidity so as not to be transformed at the time of receiving the biasing force of the clutch spring 206. In other words, it is necessary to provide an end plate 209 and the traveling plate 207, which have relatively high rigidity and thickness when using the clutch spring 206 as constituted by the compression coil spring. Therefore, there arises a problem that the clutch is large-sized.
The present invention has been devised in light of the above-described circumstances, and it is an object thereof to compactify a centrifugal clutch which is provided with a clutch release mechanism.